As a result of our discovery that nucleolin is the likely target of novel aptamer oligonucleotides with strong antitumor activity, we have become interested in the role of this protein in cancer biology. We have proposed that the tumor-selective effects of these aptamers occur because certain nucleolin functions are more critical for the survival of transformed cells than for normal cells. Elevated levels of nucleolin are already known to be associated with malignant progression and poor clinical prognosis in a variety of cancers. However, because the best characterized functions of nucleolin involve ribosome biogenesis, it is commonly supposed that this relationship merely reflects the higher proliferative activity of malignant cells. For this reason, the functional role of nucleolin in cancer has not been extensively studied. The central hypothesis of this proposal is that rather than being simply a marker for cancer, nucleolin overexpression actively contributes to the process of malignant transformation. This postulate is based in part on a number of recent studies that have identified new functions for nucleolin, many of which could potentially promote the development, survival, or progression of the malignant phenotype. In addition, preliminary data indicate that expression of antisense nucleolin mRNA in Hela tumor cells leads to reduced proliferation and suppression of anchorage-independent growth, whereas HeLa cell lines overexpressing nucleolin exhibit a more aggressive phenotype compared to wild type cells. The aim of the proposal is to test the hypothesis that overexpression of nucleolin can cause neoplastic transformation of normal cells in vitro and in vivo, This will be achieved by creating NIH3T3-derived cell lines with stable high level expression of nucleolin and generating transgenic mice that have prostate-targeted overexpression of nucleolin. Cell lines will be analyzed for standard features of malignancy such as altered morphology, increased proliferation, anchorage-independent growth, decreased sensitivity to apoptotic stimuli, enhanced migration, and tumorigenicity in nude mice. Transgenic mice will be examined histologically for malignant or pre-malignant changes of the prostate. Success in demonstrating that nucleolin overexpression functionally contributes to malignant transformation would open up new avenues for exploration in cancer research and firmly establish nucleolin as a novel target for therapeutic intervention.